The present invention relates to injection molding and die casting systems. In particular, the present invention relates to vacuum blocks and vent blocks used with injection molding and die casting systems.
Injection molding and die casting processes typically incorporate stationary and movable mold halves, which open and close along a parting line to define a cavity where the molding or casting manufacturing material is injected. Stationary mold halves, also known as fixed-die halves, fixed holder blocks, or cover blocks, are mounted to stationary platens. In contrast, movable mold halves, also known as movable-die halves, movable holder blocks, or ejector halves, are capable of moving relative to the stationary mold half for opening and closing the cavity. Movable mold halves are mounted to ejector platens, which are generally connected to hydraulic actuators for providing the movement required for ejecting the manufactured part.
Vacuum assistance in injection molding and die casting processes has been utilized to varying degrees for optimizing product quality. The general intent of the vacuum is to improve the production of injection molding and die casting by removing gases from within the molding and casting cavities. These improvements include higher surface quality, reduced level of porosity, and greater mechanical characteristics such as strength. Vacuum assistance generally requires the use of a vacuum pump, a vacuum line connecting the pump to the molding or casting cavity, and a means for preventing injected material from overflowing into the vacuum system. One approach for preventing the flow of the injected material is with an automated or manual valve located along the vacuum line. The purpose of the valve is to stop the flows of the vacuum and the injected material before the material enters the vacuum system.
An alternative approach for preventing overflow of the injected material is with gas purging blocks, such as a vacuum block or a vent block. Vacuum blocks are typically connected to the stationary and movable mold halves, and simultaneously provide a gas path for allowing the vacuum to remove the gases, and allow the excess injected material to solidify during the drawing of the vacuum. The solidified material functions as a stopper, preventing further manufacturing material from flowing out of the vacuum block and into the vacuum system. As such, vacuum blocks preclude the need for mechanical valves.
Similarly, vent blocks allow gases to be purged from the cavity of a molding or casting system by the force of the injected material flowing into the cavity. If the injected material is not stopped, it will continue to overflow out of the vent block with the purged gas. The vent block allows the injected material to solidify within the gas path during the injection process, effectively stopping-up the gas path to permit the injected material to fully fill the cavity. As with vacuum blocks, the solidified material must be ejected from the vent block along with the new product being ejected from the mold or die cavity. Typically, with both vacuum blocks and vent blocks, the overflow material that solidifies in the blocks is cut from the molded products and recycled back into the raw materials for further use.
Based upon the molding or casting process required, different vacuum blocks or vent blocks may be required. For example, manufacture of parts or components having different volumes requires mold or die cavities with different shot sizes and a vacuum or vent block with a corresponding capacity. Larger cast or mold pieces require more gas to be purged from the system, which also requires large amounts of excess injected manufacturing material to be drawn into the vent block or vacuum block. As such, there is a need in the industry for vacuum and vent blocks that have large flexibility in their ability to draw a vacuum or vent a mold, and that are also able to rapidly cool and easily eject overflow manufacturing material from the vacuum or vent block after production.